Tiltrotor aircraft typically include multiple propulsion assemblies that are positioned near the outboard ends of a wing. Each propulsion assembly may include an engine and transmission that provide torque and rotational energy to a drive shaft that rotates a proprotor assembly including a hub assembly and a plurality of proprotor blades. Typically, a pylon assembly, which includes the proprotor assembly, is rotatable relative to the wing such that the proprotor blades have a generally horizontal plane of rotation providing vertical lift for takeoff, hovering and landing, much like a conventional helicopter, and a generally vertical plane of rotation providing forward thrust for cruising in forward flight with the wing providing lift, much like a conventional propeller driven airplane. In addition, tiltrotor aircraft can be operated in configurations between the helicopter flight mode and the airplane flight mode, which may be referred to as conversion flight mode.
The propulsion assemblies of tiltrotor aircraft tend to be quite large and heavy. Accordingly, tiltrotor aircraft wings must be designed with sufficient stiffness to support the weight of the propulsion assemblies as well as withstand the forces generated by the proprotor assemblies and provide a lifting force sufficient to lift the tiltrotor aircraft during forward flight. In the event of a crash, due to the location of the wing over the fuselage, the downward inertia of the wing and propulsion assemblies has the potential to crush the fuselage and any passengers therein. If the fuselage includes any structurally compromising features underneath the wing, such as a door, then the fuselage may be even more at risk of being crushed by the wing. Accordingly, a need has arisen for an improved tiltrotor aircraft design that protects the fuselage and any passengers therein from being crushed by the wing in the event of a crash.